An existing policy for using spectrums is fixed allocation. That is, the government allocates fixed resources for a specific service of a specific user, for example, TV, radio, radar, and navigation all use fixed frequencies. Some frequencies are not used constantly and are not used in all geographic locations. Therefore, in some periods and at some geographic locations, a situation in which some frequencies fail to be fully used exists, which causes a great waste of spectrum resources. A cognitive radio (CR, Cognitive Radio) technology may detect, by cognizing a radio spectrum environment, these unoccupied frequency bands that appear anytime and anywhere, and dynamically access these unoccupied frequency bands under a premise that a primary user (Primary User, user using a fixedly allocated frequency) is not interfered. In this way, spectrum utilization is improved. Based on the current shortage situation of spectrum resources and that the CR technology has performance of improving the spectrum utilization, standard associations worldwide make great efforts to standardize the CR technology.
Two problems need to be solved for using the CR technology: 1. Accurately detect a spectrum blanking period in time; 2. Access these spectrums in the blanking period in time. In addition, a reconfigurable radio system (Reconfigurable Radio Systems, RRS) describes that various radio technologies and services exist in a future radio communication environment. A terminal may select an access technology and a carrier according to a service requirement. Work frequencies of different access technologies change anytime and anywhere. In such a complex network environment, time and power are wasted for the terminal to search for a specific access technology. Therefore, the RSS criterion group proposes a cognitive pilot channel (Cognitive Pilot Channel, PPC). This channel may be borne on an existing radio access network such as a Global System for Mobile Communications (Global System for Mobile Communications, GSM) network and may also be borne on a future radio access network. Regardless of an access network on which the channel is borne, a CPC access point (CPC Access Point, CPC AP) supports wide-scope coverage, and not only covers a large number of cells with different standards and of different carriers, but also covers cognitive cells of different types. The CPC AP periodically broadcasts spectrum utilization states and service provisioning states of different areas. Upon powering on, a terminal may quickly obtain a local available spectrum and a local offerable service from the CPC AP.
As can be seen from the foregoing, a cognitive network under CPC network architecture is a network established between a terminal with a cognition function and a base station. The terminal and the base station need to cognize the radio spectrum environment. Before establishing the cognitive network, the terminal and the base station need to exchange cognitive information, negotiate a work frequency and a broadcast channel. A function of the CPC AP is to assist the base station and the terminal in completing cognitive information exchanging, work frequency negotiation, broadcast channel selection, and so on, and finally establishing a cognitive system.
A process that is proposed for initializing the cognitive system is as follows:
A terminal and a base station are powered on, scan a CPC, and obtain a set of available spectrums from a CPC AP, that is, a set of frequencies that are not registered with the CPC AP for use.
The terminal and the base station cognize the set of available frequencies and complete assessment on each frequency; then, the base station sends a random access request to the CPC AP, obtains sending resources of a next message, and establishes a bearer with the CPC AP.
After the base station establishes the bearer with the CPC AP, the base station sends a cognitive message to the CPC AP, including a cognition result, a base station identify (Identity, ID), and geographic location information. The base station is required to support a positioning technology, for example, a Global Position System (Global Position System, GPS).
After receiving the message of the base station, the CPC AP broadcasts the received cognition result on a CPC broadcast channel.
The terminal obtains information about all base stations around the terminal according to the broadcast information, and judges, according to the geographic location information, whether the base station is within its communication scope and satisfies its service requirement. After assessment, if the terminal expects to establish a network with a particular base station, the terminal first sends a random access request to the CPC AP, obtains sending resources of the next message, and establishes a bearer with the CPC AP.
After establishing the bearer with the CPC AP, the terminal sends messages such as a spectrum cognition result and a target base station ID to the CPC AP. As the terminal does not establish a work frequency with the base station, the terminal notifies, only through the CPC AP, the base station that the terminal expects to establish a network with the base station.
The CPC AP sends the cognition result of the terminal to a target base station according to the target base station ID.
After receiving the cognition result of the terminal, the base station first converges cognitive data to obtain a cognitive decision, where the cognitive decision includes a work frequency and a broadcast channel used by the base station on the network, and sends the cognitive decision result to the CPC AP.
The CPC AP sends the cognitive decision to the terminal.
If the terminal does not satisfy with the decision result, the terminal continues to send a cognitive message to the CPC AP, including the cognition result, the base station ID, an expected work frequency, and so on. The CPC AP sends the message of the terminal to the base station so that the base station adjusts the cognitive decision.
If the terminal satisfies with the decision result, the terminal sends a confirmation message to the base station and the CPC AP. The CPC AP releases the bearer with the base station and releases the bearer with the terminal.
The terminal and the base station are switched over to the work frequency specified in the decision result and establish a channel.
During the implementation of the present invention, the inventor discovers that:
As the base station ID is introduced, the ID may be a unique ID on the whole network and a value of the ID may be very large, system implementation complexity increases. After the terminal knows the base station ID, as the terminal and the base station do not know a communication capability and scope of each other, both the base station and terminal need to support the positioning technology. After the positioning technology such as the GPS is introduced, system costs may increase because the GPS is expensive.